For example, in the case of forming external electrodes of chip-type electronic components, methods are widely used in which a paste-like electroconductive paste obtained by kneading an electroconductive constituent with glass frit, an organic vehicle, etc. is applied and baked.
Further, as such an electroconductive paste, for example, an electroconductive paste for external electrodes has been proposed which contains at least spherical and flake copper powders and glass frit, and forms an external electrode by application to a predetermined surface of a chip-type electronic component, such that the average particle sizes of the spherical and flake copper powders both fall within the range of 3 to 10 μm, and the electroconductive paste has a film density of 4.0 g/cm3 or more (see Patent Document 1).
In addition, as an electroconductive paste that is used for the formation of external electrodes in a step for manufacturing a ceramic electronic component structured to have external electrodes provided on a ceramic element, an electroconductive paste has been proposed which contains: a metal powder containing, as its main constituent, a Cu powder obtained by blending a flake Cu powder that meets the requirements of 0.5 to 1.0 m2/g in specific surface area, 20 to 40 μm in longest diameter B, and 0.05 to 3 μm in thickness T, and a spherical Cu powder in predetermined proportions; a glass powder; a binder; and an organic solvent (see Patent Document 2).
Furthermore, an electroconductive paste containing an inorganic powder and an organic vehicle has been proposed which is baked to form external electrodes for laminated ceramic electronic components, where the inorganic powder contains a metal powder composed of Cu or a metal powder containing Cu as its main constituent, glass frit, and a titanium oxide powder, the proportion of the glass frit is 15% by volume to 30% by volume with respect to 100% by volume of the metal powder, the proportion of the titanium oxide powder is 0.5% by volume to 6.0% by volume with respect to 100% by volume of the metal powder, and the glass frit is further 1.4 Pa·s to 3.1 Pa·s in viscosity log η at a baking temperature (see Patent Document 3).
While various types have been proposed as electroconductive pastes as described above, these electroconductive pastes are all electroconductive pastes for the formation of external electrodes for chip-type electronic components, but not intended for use in bonding metal terminals to external electrodes formed on electronic component elements (electronic component bodies).
Therefore, when these pastes are used for bonding metal terminals, it is actually difficult to achieve intended bonding characteristics such as desired bonded conditions and bonding strength.
For example, when the electroconductive pastes in Patent Documents 1 and 2 are used to bond metal terminals to external electrodes formed on end surfaces of electronic component elements, there are problems as explained below.
More specifically, for bonding metal terminals to external electrodes formed on end surfaces of electronic component elements, for example, when a method is applied in which the metal terminals are bonded to the external electrodes by baking the electroconductive paste while the metal terminals are pushed against the external electrodes with the electroconductive paste interposed therebetween, the electroconductive paste located between the metal terminals and external electrodes will be spread out to lose the ability to sufficiently ensure the amount of the electroconductive paste existing between the metal terminals and the external electrodes, thus resulting in an insufficient fixing strength of the fired metal terminals to the external electrodes, and resulting in a problem of failure to achieve any highly reliable electronic component with metal terminals.
In addition, even if a certain level of bonding force (fixing force) is achieved, because of the low amount of baked electrodes (bonding electrodes) located between the metal terminals and the external electrodes to provide the bonding force, the difference in linear coefficient of expansion between an electronic component element (for example, a ceramic body) as a base material and the metal terminal is not able to be absorbed sufficiently by the baked electrode, and there is the problem of crack generation in the baked electrode itself, the ceramic body, etc. in a thermal shock test.
In addition, even in the case of using the electroconductive paste in Patent Document 3, because of the inability to hold the electroconductive paste in a sufficient amount between metal elements and external electrodes, the difference in linear coefficient of expansion between an electronic component element (for example, a ceramic body) and the metal terminal is not able to be sufficiently absorbed by the baked electrode (bonding electrode), and there is the problem of crack generation in the baked electrode itself, the ceramic body, etc. in a thermal shock test.    Patent Document 1: Japanese Patent Application Laid-Open No. 2001-338830    Patent Document 2: Japanese Patent Application Laid-Open No. 2004-172383    Patent Document 3: Japanese Patent Application Laid-Open No. 2003-297146